OneUptime has WebAuthn 2FA bypass: server accepts client-supplied challenge instead of server-stored value, allowing credential replay

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.2 · CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N

EPSS

• CVE-2026-28787: 0.31% estimated exploitation activity in the next 30 days; percentile 24.39 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The WebAuthn authentication implementation does not store the challenge on the server side. Instead, the challenge is returned to the client and accepted back from the client request body during verification. This violates the WebAuthn specification (W3C Web Authentication Level 2, §13.4.3) and allows an attacker who has obtained a valid WebAuthn assertion (e.g., via XSS, MitM, or log exposure) to replay it indefinitely, completely bypassing the second-factor authentication. Details During WebAuthn authentication, the server generates a random challenge via generateAuthenticationOptions() in Common/Server/Services/UserWebAuthnService.ts (line 164-221). However, the challenge is only returned to the client and never stored in a session or database on the server side. When the client submits the authentication response, the server reads the expectedChallenge directly from the untrusted request body (Authentication.ts:1042): The verifyAuthentication() method then passes this…

Published by the source

2 Mar 2026, 21:40 UTC

Last modified by the source

6 Mar 2026, 15:31 UTC

Source last checked

26 Oct 2026, 12:43 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-gjjc-pcwp-c74m

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-gjjc-pcwp-c74m

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# Patch Next advisory brief: CVE-2026-28787

Advisory: OneUptime has WebAuthn 2FA bypass: server accepts client-supplied challenge instead of server-stored value, allowing credential replay
IDs: CVE-2026-28787, GHSA-gjjc-pcwp-c74m
Record: https://patchnext.com/advisories/cve-2026-28787 (revision 2, source checked 26 Oct 2026, 12:43 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @oneuptime/common: affected <= 10.0.11

## Suggested inspection (read-only)
- `npm ls @oneuptime/common --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @oneuptime/common.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-gjjc-pcwp-c74m (OSV record GHSA-gjjc-pcwp-c74m lists affected ranges: npm @oneuptime/common >=0 <=10.0.11)
- Verified: https://github.com/advisories/GHSA-gjjc-pcwp-c74m (GitHub-reviewed advisory GHSA-gjjc-pcwp-c74m lists affected ranges: npm @oneuptime/common >=0 <=10.0.11)

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